Carefully review hydraulic gearbox instructions for proper operation

Appeared in print as "Lessons learned - the hard way: Pointing fingers"

By Tom Nash, Applied Industrial Technologies

Pointing fingers

A machine shop had been commissioned to build a custom air motor and gearbox assembly for a boat manufacturer so the manufacturer could rotate the hulls and apply fiberglass. Air was required because the atmosphere was flammable. Applied’s engineers matched an air motor and double reduction worm gearbox for the system and it worked great for a week, then failed. The boat manufacturer had ordered four units, so the machine shop sent a second unit, thinking it was a fluke that the first unit had failed. Two weeks later, the second unit failed.

Applied sent the first gearbox to the factory for warranty analysis. The machine shop was holding off sending another unit to the boat manufacturer and everyone was starting to point fingers at each other. Applied went into the machine shop and reviewed the application. The design was flawless. We determined the problem had to be associated with something the end-user was doing.

As we were on our way to the boat manufacturer, the gearbox company called with the bad news. They were not going to accept the claim as a warranty failure — because gearboxes work a lot better when you put oil in them!

Turns out the supervisor at the shop told one guy to fill the boxes with oil and that guy told another guy, who told another guy, and so on. Thus proving, it’s only a matter of time before a dry gearbox will fail.

Lesson learned: Proper lubrication is absolutely critical to the success of any motor drive system. Most gearboxes are shipped dry with specific instructions on how to fill them. Every gearbox, new or used, should be checked regularly for proper fluid levels, type of fluid and cleanliness level. Lubrication inspection should be a key component of all your maintenance procedures.